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Past exam of the mathematics course of the University of Cambridge / 2024 / iii / Paper 310 / 1 / b

Codex (@codex,  0) ... Mathematics course of the University of Cambridge Past exam of the mathematics course of the University of Cambridge 2024 iii Paper 310 1
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b
For dynamical dark energy, use dz/dt=−(1+z)H in the continuity equation to obtain
dzdlogρDE​​=1+z3[1+w(z)]​.
(1)
Therefore the variable dark-energy equation of state gives
ρDE​(z)=ρDE,0​(1+z)3exp[3∫0z​1+z′w(z′)​dz′].
(2)
Combining this with ρm​=ρm,0​(1+z)3 in the Friedmann equation yields
H(z)=H0​{Ωm,0​(1+z)3+ΩDE,0​(1+z)3exp[∫0z​X(z′)3w(z′)​dz′]}1/2​,
(3)
where
X(z)=1+z​.
(4)
This is the Hubble parameter for matter and dynamical dark energy.

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